Unknown device keeps attaching itself onto router?!

I really don't know what this device is. It shows up as 'Unknown-01-02-03...'. I disconnected everything from the router by changing the Wifi password. I re-connected with only my phone and that unknown device has somehow connected also. What is going on?

Re: Unknown device keeps attaching itself onto router?!

You could try changing the wifi password in the router (note is down), then you will have to change them in all of your devices which connect via wifi. Unknown, simply means the device is not fully identifying itself.